Selected in 2013 for a 2020 launch, the spacecraft will operate in the deep space radiation environment throughout its 18-month mission.[4] This will help scientists understand the health threat from cosmic rays and deep space environment on living organisms and reduce the risk associated with long-term human exploration, as NASA plans to send humans farther into space than ever before.[3][4]

The mission is being developed by NASA in collaboration with some universities.

The primary objective of BioSentinel is to develop a biosensor using a simple model organism (yeast) to detect, measure, and correlate the impact of space radiation to living organisms over long durations beyond low Earth orbit (LEO) and into heliocentric orbit. While progress has been made with simulations, no terrestrial laboratory can duplicate the unique space radiation environment.[3][4]

The BioSentinel biosensor uses the budding yeastSaccharomyces cerevisiae to detect and measure double-strand breaks (DSBs) on DNA that occur in response to ambient space radiation.[6] This yeast strain was selected because its DSB repair mechanisms are well studied and are very similar to those in human cells.[1] The biosensor consists of specifically engineered yeast strains and nutrient selection strategies that ensure that only cells that can repair their DSBs will grow in specialized media. Therefore, culture growth and metabolic activity of yeast cells directly indicate a successful DSB-and-repair event.[1][4]

After completing the Moon flyby and spacecraft checkout, the science mission phase will begin with the wetting of the first set of yeast-containing wells with specialized media.[4] Multiple sets of wells will be activated at different time points over the 18-month mission. One reserve set of wells will be activated in the occurrence of a solar particle event (SPE). Approximately, a 4 to 5 krad total ionizing dose is anticipated.[1][7] Payload science data and spacecraft telemetry will be stored on board and then downloaded to the ground.[4]

The Biosentinel spacecraft will consist on a 6U CubeSatbus format, with external dimensions of 10×20×30 cm and a mass of about 14 kg (31 lb).[1][3][4][8][9] At launch, BioSentinel resides within the second stage on the launch vehicle from which it is deployed to a lunar flyby trajectory and into an Earth-trailing heliocentric orbit.

Of the total 6 Units volume, 4 Units will hold the science payload, including a radiation dosimeter and a dedicated 3-color spectrometer for each well; 1U will house the ADCS (Attitude Determination and Control Subsystem) and 1U will house the attitude control thruster assembly, which will be 3D printed all in one piece: cold gas (DuPont R236fa) propellant tanks, lines and seven nozzles. The use of 3D printing also allows the optimization of space for increased propellant storage[10] (165 grams[6]). The thrust of each nozzle is 50 mN, and a specific impulse of 31 seconds.[10] The attitude control system is being developed and fabricated by the Georgia Institute of Technology.